An accelerometer measures proper acceleration, which is the acceleration it experiences relative to free fall. Proper acceleration is associated with the phenomenon of weight experienced by a proof mass that resides in a frame of reference of the accelerometer. An accelerometer measures the weight per unit of the proof mass, a quantity also known as specific force, or g-force. Conceptually, an accelerometer behaves as a damped mass on a spring. When the accelerometer experiences acceleration, the position of the proof mass is displaced with respect to the frame. The displacement is measured to determine the acceleration.
Accelerometers can be applied to inertia navigation, seismometry and a wide variety of diagnostic and instrumentation applications. For example, an accelerometer can be used to evaluate the performance of both the engine/drive train and the braking system of a vehicle.
Recent development in Micro-Electrical-Mechanical Systems (MEMS) technology has made it possible to build MEMS accelerometers (also called micromachined accelerometers). These micromachined accelerometers can be used in a wide variety of small-size light-weight handheld devices. However, there is a continuing need for the micromachined accelerometers to have high resolution and low noise.